Introduction: The effect of a-particle irradiation on AlGaAsIGaAs heterostructures has been studied by many investigators [l to 31. In the present note we study the effect of 2.84 MeV a-particle irradiation on the properties of AlGaAs/GaAs heterostructures by measurements of photoconduction current as a function of the wavelength at various temperatures from 200 to 350 K before and after irradiation. Experimental techniques The AlGaAsIGaAs specimen consisted of eight layers as follows: first layer 100 nm undoped GaAs; second, fourth, and sixth layers 10 nm AlGaAs; third and fifth layers 10 nm GaAs; seventh layer 200 nm GaAs; eighth layer semi-insulating GaAs substrate. Two semicircular gold contacts were formed by evaporation on the first layer. The distance between them is 100 pm. The illumination reached the surface of the first layer. The current was measured by a Carry vibrating reed electrometer. The specimen was enclosed in the cryostat of a gas helium circulated machine and the window of the cryostat was closed by a Mylar sheet of 12 pm thickness. The total dose of a-particles from a 0.6 mC Am source was 8.94 x 10’’ and 4.77 x 10” particles/cm’ for specimens No. 3 and No. 4, respectively. Specimen No. 3 was irradiated at T = 200 K, while specimen No. 4 at T = 293 K. We calculated the range of the 2.84 MeV a-particles inside GaAs in the direction to the vertical to the surface according to the Geiger rule and found it equal to 6.4 pm. This means that the a-particle goes through the whole specimen. Results and discussion In Fig. 1 the photocurrent spectra for various temperatures are shown before irradiation (a) and after irradiation at 293 K and annealing at 350 K (b). The peak of the spectrum taken at 293 K is almost the same as that of the spectrum of the same structure (except of some small differences in the thickness of the layer) taken at 200 K [4]. After a-particle irradiation at 293 K the photocurrent peak is shifted to 880 nm (Fig. 1 b) and a decrease of the photocurrent at the peak of about 60% is observed. A greater shift has been found after electron irradiation of almost the same structure [4]. As the temperature decreases, the peak is shifted to smaller wavelengths and appeared at 200 K at the same wavelength as before irradiation (Fig. la, b). As the temperature is lowered from 293 to 200 K, the photocurrent at the peak decreases four times before irradiation and three times after irradiation.